The cross-metathesis of ethylene and internal olefin to produce alpha-olefins is generally referred to as ethenolysis. Olefins Conversion Technology™, based upon the Phillips Triolefin Process, is an example of an ethenolysis reaction converting ethylene and 2-butene into propylene. These processes uses heterogeneous catalysts, such as tungsten and rhenium oxides, which have not proven effective for internal olefins containing functional groups such as cis-methyl oleate, a fatty acid methyl ester.
Methods for the production of polyalpha-olefins are typically multi-step processes that often create unwanted by-products and waste of reactants and energy. Full range linear alpha-olefins plants are petroleum-based, are inefficient and result in mixtures of oligomerization products that typically yield Schulz-Flory distributions producing large quantities of undesirable materials. In recent years there have been new technologies implemented to produce “on purpose” linear alpha-olefins such 1-hexene and 1-octene through chromium-based selective ethylene trimerization or tetramerization catalysts. Alternatively, 1-octene has been produced via the telomerization of butadiene and methanol. Similar strategies are not currently available for the production of 1-decene.
1-Decene is a co-product in the cross-metathesis of ethylene and methyl oleate. Alkyl oleates are fatty acid esters that can be major components in biodiesel produced by the transesterification of alcohol and vegetable oils. Vegetable oils containing at least one site of unsaturation include canola, soybean, palm, peanut, mustard, sunflower, tung, tall, perilla, grapeseed, rapeseed, linseed, safflower, pumpkin corn and many other oils extracted from plant seeds. Alkyl erucates similarly are fatty acid esters that can be major components in biodiesel. Useful biodiesel compositions are those which typically have high concentrations of oleate and erucate esters. These fatty acid esters preferably have one site of unsaturation such that cross-metathesis with ethylene yields 1-decene as a co-product.
Biodiesel is a fuel prepared from renewable sources, such as plant oils or animal fats. To produce biodiesel, triacylglycerides (“TAG”), the major compound in plant oils and animal fats, are converted to fatty acid alkyl esters (“FAAE,” i.e., biodiesel) and glycerol via reaction with an alcohol in the presence of a base, acid, or enzyme catalyst. Biodiesel fuel can be used in diesel engines, either alone or in a blend with petroleum-based diesel, or can be further modified to produce other chemical products.
Cross-metathesis catalysts reported thus far for the ethenolysis of methyl oleate are typically ruthenium-based catalysts bearing phosphine or carbene ligands. Dow researchers in 2004 achieved catalysts turnovers of approximately 15,000 using the 1st generation Grubb's catalyst, bis(tricyclohexylphosphine)benzylidene ruthenium(IV) dichloride, (Organometallics 2004, 23, 2027). Researchers at Materia, Inc. have reported turnover numbers up to 35,000 using a ruthenium catalyst containing a cyclic alkyl amino carbene ligand, (WO 2008/010961). These turnovers were obtained with a catalyst reportedly too expensive for industrial consideration due to high costs associated with the catalysts being derived from a low yielding synthesis (See Final Technical Report entitled “Platform Chemicals from an Oilseed Biorefinery” grant number DE-FG36-04G014016 awarded by the Department of Energy). In order to obtain an economically viable process for 1-decene production via the cross-metathesis of ethylene and biodiesel or vegetable oils, higher activity catalysts must be discovered. Thus there is a need for higher activity processes that produce desired products and co-products in commercially desirable ratios.
Likewise, there is a need to develop a means to provide linear alpha-olefins (particularly high yields of linear alpha-olefins) by metathesis reactions, particularly reactions with good conversion, preferably under mild reaction conditions is a minimal number of steps. The instant invention's metathesis catalyst provides both a commercially economical and an “atom-economical” route to linear alpha-olefins.
Specifically, the instant inventors have found that the combination of a cyclic alkyl amino carbene ligand attached to ruthenium with a chelating benzylidene ligand containing an electron withdrawing group yielded a catalyst that is both highly active and very selective towards the ethenolysis of methyl oleate yielding 1-decene and methyl-9-decenoate.